The present invention is directed to a sorting unit for a switching node comprising a plurality of digital switching matrix networks for fast, asynchronous packet switching networks, whereby the switching node comprises a multistage, mixed connection structure, for instance in the fashion of what is referred to as a banyan tree structure, that forms a complete trunk group, namely such that every input of the switching node is connectable to every output thereof.
In future broad band ISDN (integrated switching digital networks), services such as "picture telephony", "video conferencing" and data communication with a high bit rate should be integrated therein in addition to the classic applications of "telephony" and "narrow band data transmission". Therefore, there is a necessity for different channels having different bit rates, for instance 64 kbit/s for telephony and 2-10 Mbit/s for "picture telephony" and "video conferencing".
In data communication, data streams having bit rates of 2-10 Mbit/s are also to be switched that, however, appear in batches (burst mode) and comprise such large gaps that the physical through-connection therefor in one line section is extremely ineffective. Therefore, the transmission and switching equipment would be only utilized at a low level of efficiency, but would have to remain reserved for availability when needed.
Packet switching systems (using a fast packet switch) are therefore planned for the switching of the data applications with a high bit rate, these packet switchings working faster and with simpler protocols when contrasted to the present "Datex-P-Network". These switchings that through-connect the high-bit-rate data streams without intermediate protection are also suitable for the switching of the other applications and thus open up the way to an actual integration of different communications applications in a common network.
As a consequence of the high processing capacity, the "fast packet" switching node should be constructed of components that work in a decentralized manner and that form the structure of a node in a multi-stage arrangement. Possible structures are derived from a simple, so-called banyan network and differ in such fashion that inner blockings are reduced or avoided. A distinction is generally made between packet-synchronous and packet-asynchronous switching nodes. Whereas synchronous, blocking-free switching nodes are known from the literature, the problem of inner blockings in asynchronous methods has not yet been satisfactorily resolved.